Adult Health Library

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Disorders of Sex Development

When a child's gender is in question at birth, the child has atypical genitalia (ambiguous genitalia). This means that the genitals may not appear to be clearly male or female.

Atypical genitalia can be a difficult experience for families.

How do the reproductive organs form?

You have 46 chromosomes in each cell of your body. These are grouped into 23 pairs. The 23rd pair determines your gender. Females have two X chromosomes, and males have one X and one Y chromosome.

The gender of a developing baby is determined at conception, when the embryo has either two XX chromosomes, or an X and a Y chromosome. Around the 6th week of fetal development, a gene on the Y chromosome of a developing boy tells the fetal tissue that will form the sex organs to become the testes.

As the testes make testosterone, the penis, scrotum, and urethra form. Then, during the 7th to 8th month of the pregnancy, the testes descend into the scrotum.

Without the Y chromosome, the fetal tissue in a female fetus that will form the sex organs becomes the ovaries, uterus, and fallopian tubes.

Certain hormones also can affect the development of the sexual organs. These hormones are secreted during the early weeks of gestation.

How do disorders of sexual development happen?

A variety of genetic and environmental factors can affect the developing baby and lead to atypical genitalia. Ambiguous genitalia may make it more difficult to determine a baby’s gender. But very few newborns with this condition have genitals that are so ambiguous that the healthcare provider can’t determine the gender at birth.

These are far more common at birth:

A girl baby with too much of the male hormones (virilization) who seems to have a small penis

A boy baby with an abnormally small penis that looks like a female clitoris. This is either because the fetus did not respond to male hormones or the fetus did not make male hormones.

What causes atypical genitalia?

Atypical genitalia can have a number of different causes. In many cases, doctors don’t know the cause, and it seems to occur by chance.

Children who are born with atypical genitalia may fall into one of the following groups.

True hermaphroditism

These children have:

Tissue that is related to both the ovaries and the testes

Internal sex organs for both genders

External genitalia that are partly ambiguous

Chromosomes that are either normal female or male, or a mixture (mosaic)

Gonadal dysgenesis

These children have:

An undeveloped sex organ

Internal sex organs that are usually female

External genitals that may vary between normal female and normal male. Most are female.

Chromosomes that are normal, have only a X chromosome, or are a mixture (mosaic)

Pure gonadal dysgenesis

Pseudohermaphroditism in males

Children with this condition have questionable external genitalia, but have only one gender's internal sex organs. Male pseudohermaphrodite means the child has internal sex organs that are male. Female pseudohermaphrodite means the child has internal sex organs that are female.

The two primary causes of male pseudohermaphroditism are androgen insensitivity syndrome and 5-alpha reductase deficiency.

Androgen insensitivity syndrome

These children have:

Normal male chromosomes

Normal female external genitalia

This is called androgen insensitivity syndrome because male babies don’t respond to testosterone (androgens). This syndrome is inherited. It is caused by a problem with a gene on the X chromosome. This problem is called X-linked recessive. Mothers who carry the gene have a 50% chance of having a son with the syndrome. Daughters of mothers who carry the gene have a 50% chance of being carriers of the gene.

5-alpha-reductase deficiency

Children with this condition have:

Normal male chromosomes

Genitals that are ambiguous

Children with this condition lack the enzyme 5-alpha reductase. This enzyme is needed to help the male sex organs complete their development. This condition is inherited. It is caused by an autosomal recessive gene. Autosomal recessive means that each parent carries one copy of the gene and transmits the gene at the same time to the child. Carrier parents have a 1 in 8 chance of having a child with this condition with each pregnancy. It affects only male babies.

Pseudohermaphroditism in females

Female pseudohermaphroditism has a number of causes.

Congenital adrenal hyperplasia (CAH)

Girl babies with this condition have male sex organs. The condition is caused by a lack of a certain enzyme in the adrenal gland. It is the most common cause of atypical genitalia in newborns.

The condition is inherited and passed on by an autosomal recessive gene. Autosomal recessive means that each parent carries one copy of the gene and passes on the gene to the child. Carrier parents have a 1 in 4 chance of having a child with this condition with each pregnancy. Girl babies with the condition have atypical genitalia. Boy babies do not.

In some cases, the mother of a child with this condition can be given medicines during pregnancy to lessen the effects of the enzyme deficiency if the fetus is female.

Another type of CAH is called "salt-losing." This is very serious and often fatal. It causes an electrolyte collapse in the newborn. Treatment is available if diagnosed early. Boys and girls are equally affected.

Other, rarer enzyme problems can also cause CAH in either boy babies or girl babies.

Overproduction of male hormones before birth

This condition is often caused by a problem with the adrenal glands. High levels of male hormones may also enter the placenta via the mother. This could be when the mother is given progesterone to prevent a miscarriage or if she has a hormone-producing tumor.

How is the gender determined in a child with atypical genitalia?

When a child's genitalia appear ambiguous at birth, your child's healthcare provider will ask about your health history. The health history will include your health during pregnancy and a family history of any neonatal deaths or genital abnormalities. The provider will also do a physical exam of your child's external genitalia.

Your child's provider will look for the underlying cause of the disorder. Your child may need a newborn screening test for CAH, hormone studies, and a biopsy of the sex organs.

To determine the sex, your child's healthcare providers will consider the following:

A pelvic ultrasound to check for the female sex organs. Or the provider may use direct cystoscopy or vaginoscopy.

A genitourethrogram to look at the urethra and vagina, if present

A chromosome study to help determine the genetic sex of the child

Evaluation of gene on the Y chromosome that starts development of the male sex organs

How fertile a child may be who is a female pseudohermaphrodite

Size and potential for growth of a penis present in a male pseudohermaphrodite

Ability of an internal sex organ to make the appropriate sex hormones for the gender "assigned" to the child

Risk of future health conditions such as cancer that may develop in the original sex organs later in life

The actions of male or female hormones on the fetal brain

Your opinion or preference

Treatment for atypical genitalia

Sometimes a child with atypical genitalia is at higher risk for tumors in the sex organs. Treatment for atypical genitalia depends of the type of the disorder, but will usually include surgery to remove or create sex organs appropriate for the gender of the child. Treatment may also include hormone therapy.

Most important, you and your family should be involved early in the decision of assigning the sex of the child. Ask your healthcare provider about what is available for long-term psychological support.

Long-term outlook for children born with atypical genitalia

Making a correct determination of gender is important for treatment. But is also important for the emotional well-being of the child. Some children born with atypical genitalia may have normal internal sex organs that allow them to live normal, fertile lives. But others may have problems with fertility as adults.

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